The invention relates to an anti-locking brake control system for a motor vehicle. The system is of the type comprising wheel speed sensors for determining the speeds of the individual vehicle wheels, an evaluation circuit which receives the wheel speed signals and generates brake pressure control signals, and a brake pressure control valve responsive to the brake pressure control signals for controlling the brake pressure applied to the wheels.
In anti-locking brake systems in which brake pressure is built up in pulses so as to achieve a flat average rate of pressure increase, it is known to make the initial brake-pressure pulse after an instability greater than the pulses that follow. This can be seen in FIG. 1.
In FIG. 1, the duration T0 of the pressure rise time is dependent on the number of such pulses or on the pressure build-up time which was necessary in the preceding control cycle to cause the wheel to become unstable. The holding time T.sub.H either has a fixedly pre-established length, or else it is the time considered to be optimum, and this time T.sub.H is determined through a learning process.